This has so far been unsuccessfully attempted.
Unfortunately, no effective filters can be installed.
It is a structural problem affecting all airlines worldwide.
Since the aircrafts cannot be modified, they have to fly on because they are the business basis of the airlines in order to earn money. They cannot simply be parked for economic reasons just because they pose a health hazard. This would disrupt an entire industry. Aviation is a key industry in the German economy.
So the danger is played down or denied. The risk is accepted because it cannot be changed technically.
It applies to all aircraft with bleed air from the engines (approximately 99% of all passenger / cargo aircraft).
Even the new Airbus A380 did not take this problem into account in its design. The only exception is the new Boeing 787, the Dreamliner, which has an external tapped air system.